ANALYTICAL MECHANIC'S
which distinguishes the pivot from the journal bearing is
this: in the former the lever arm of the Motional force varies
from point to point, while
in the latter it is constant
and equals the radius of the
shaft.
Let dN be the normal reaction upon dA, an element of area at the base of the flat-end pivot of Fig. 39; then if dF denotes
y
the corresponding frictional |£ force, we h&ve
where p is the normal pressure. Evidently p is constant; therefore we can write
ra*
dA
PICK 31).
The expression for the resisting torque due to the friction is obtained as follows :
XF r-dF .
XA r*np
n2?r r/rp- rdO*dr -
= f
where P is the total load on the pivot.